Experiment. The experimental verification of the prediction of high T\(_c\)  in the yttrium hydride YH\(_9\)  was announced[1]} in 2019, and published in 2021: Kong et al.[2]}, T\(_c\) =243K at 200 GPa in space group \(P6_3/mmc\) , with the expected structure being clathrate-like.
The compound YH\(_{10}\)  predicted to have higher T\(_c\)  was not observed in their experiments, which covered certain regions of phase space up to 410 GPa and 2250K.
Snider et al. in 2021 provided data[3]} indicating T\(_c\)  up to 262 K for a sample with superconducting phase of stoichiometry likely close to YH\(_9\)  based on Raman data. This maximum T\(_c\)  occurred around 180 GPa. Extension and some degree of confirmation was provided when T\(_c\) =253K was obtained in (La,Y)H\(_n\)  mixtures by Semenok et al.[4]}
